Description: This
native perennial wildflower is 2–3½' tall, sometimes branching in the
upper half. The stems are light green and usually hairless; however,
some variants of this species have pubescent stems. Alternate compound
leaves occur at intervals along the stems; they are trifoliate and
their leaflets are extended horizontally in relation to the ground.
Individual leaflets are up to 3½" long and ¾" across; they are 3-6
times as long as they are wide. Some variants of this species have more
narrow leaflets than others. The terminal leaflet is the same length or
a little longer than the lateral leaflets. The leaflets are elliptic to
oblong in shape and smooth along their margins. Their upper surfaces
are medium green and glabrous, while their lower surfaces are pale to
medium green and covered with appressed white hairs. The petioles of
the compound leaves are up to 2" long, light green, and mostly
hairless. At the base of each petiole, there is a pair of tiny
deciduous stipules that are linear-lanceolate; these stipules soon
wither away. The petiolules (secondary petioles) of the lateral
leaflets are very short (1/8" or less), while the petiolules of the
terminal leaflets are longer (up to ½").

The upper stems
terminate in either racemes or narrow panicles of flowers. The branches
of each inflorescence are light green and covered with hooked hairs.
Individual flowers are ¼" long (or a little more), consisting of 5
petals, a short tubular calyx with teeth, an ovary with a single style,
and several hidden stamens. The flowers have a typical pea-like
structure, consisting of an upright banner and 2 lateral wings that
enclose a central keel. The petals are pink to rosy pink; at the base
of the upper petal (banner), there are 1-2 tiny patches of yellow. The
green calyx is covered with hooked hairs. The slender petioles of the
flowers are about ½" long; they are green to reddish purple and also
covered with hooked hairs. The blooming period occurs from mid-summer
to early fall and lasts about 1–1½ months. There is no noticeable
floral scent. Fertile flowers are replaced by flat loments (a type of
seedpod) that are about ½–1½" long. Each loment consists of 2-6 rounded
segments, a short stipe, and sometimes a short beak. Each segment of a
loment is more rounded along the bottom than along the top; it contains
a single seed. The loments are covered with hooked hairs. The root
system consists of an elongated caudex with fibrous roots. This
wildflower spreads by reseeding itself.Cultivation:
The preference is partial sun, mesic to dry-mesic conditions, and sandy
or rocky soil.

Range & Habitat:
Panicled Tick Trefoil is occasional in all areas of Illinois, except
the NW section, where it is rare or absent (see Distribution
Map). Habitats consist of thinly wooded bluffs, rocky open
woodlands, sandy open woodlands, sandy savannas and typical savannas,
woodland edges, thickets, rocky glades, and partially shaded roadside
embankments. This wildflower is a pioneer species that prefers some
disturbance from wildfires, selective logging, and others causes.

Faunal Associations:
Long-tongued bees collect pollen from the flowers; these relatively
uncommon floral visitors include bumblebees (Bombus spp.), leaf-cutting
bees (Megachile spp.), and long-horned bees (Melissodes spp.). Other insects
feed on the leaves, flowers, and seeds of Desmodium spp.
(Tick Trefoils). For example, the caterpillars of several skippers feed
on the leaves: Achalarus lyciades (Hoary Edge), Epargyreus
clarus (Silver-Spotted Skipper), Thorybes bathyllus
(Southern Cloudywing), and Thorybes pylades
(Northern Cloudywing). The caterpillars of the butterfly Everes
comyntas (Eastern Tailed Blue) also feed on the foliage,
while the caterpillars of the butterfly Strymon melinus
(Gray Hairstreak) eat the flowers and developing seedpods. These insect
feeders include many kinds of beetles, and some species of thrips,
aphids, moth caterpillars, and stinkbugs (see Insect
Table). The seeds are eaten by some upland gamebirds
(Bobwhite Quail, Wild Turkey) and small rodents (White-Footed Mouse,
Deer Mouse), while the foliage is readily eaten by White-Tailed Deer
and other hoofed mammalian herbivores. The Cottontail Rabbit also
consumes the foliage. The sticky seedpods (loments) cling to the fur of
animals and the clothing of humans. As a result, the seeds are carried
to new locations.

Comments:
Among different populations of Panicled Tick Trefoil, there is
significant variation in the width of the leaflets and the hairiness of
the stems and leaflets. Usually, this wildflower has fairly narrow
leaflets, hairless to nearly hairless stems, and hairless upper
surfaces on the leaflets. It can be distinguished from other species in
this genus by considering the following key characteristics: 1) the
narrow leaflets are 3-6 times longer than they are across, 2) the
petioles of the trifoliate leaves are fairly long (up to 2"), 3) the
deciduous stipules of the trifoliate leaves are small and
insignificant, and 4) the leaflets are rather long (up to 3½").
Panicled Tick Trefoil is one of the more common species of this genus
in Illinois.